Electro-mechanical drive mechanism for an impeller shroud of a variable water pump

ABSTRACT

An external actuator for a variable water pump is provided having a housing and variable flow impeller located therein that is connected to a drive shaft. The actuator includes a housing and a drive ring rotatably mounted therein, with the drive ring having external teeth and an internal thread. A drive gear is engaged with the external teeth of the drive ring, with the drive gear being rotatably mounted in the housing. A drive nut having external threads is located within the drive ring with the external threads engaging the internal threads of the drive ring. Rotation of the drive ring causes an axial displacement of the drive nut. At least one actuator pin is connected to the drive nut and extends into the water pump housing to the variable flow impeller. A motor is connected to the drive gear for rotation of the drive gear to vary an output.

INCORPORATION BY REFERENCE

The following documents are incorporated herein by reference as if fully set forth: U.S. Provisional Patent Application No. 62/033,161, filed Aug. 5, 2015.

FIELD OF INVENTION

The present invention relates to an electro-mechanical drive mechanism suitable for use in variable actuation of an impeller assembly of a variable flow water pump for an internal combustion engine.

BACKGROUND

In automotive applications, there is a push for energy efficiency. Efficiencies can be gained for example, by having a water pump which is deactivated upon cold starting of an engine so that the engine can come up to the running temperature more quickly. Known systems for deactivating a water pump include an impeller assembly with a moveable cover or shroud which covers the vanes of the pump impeller when a flow of coolant from the water pump is not desired. However, in such known systems, an internal actuator has been typically used, requiring the water pump to be substantially re-designed to include special seals for the actuator fluid, and or a separate pump for the actuator if the coolant being moved by the water pump is also used as the drive fluid for the actuator. These are complex mechanisms that require major modifications to the water pump as well as additional space requirements.

Additionally, as the water pump speed is directly correlated to the speed of the engine, the flow from a standard water pump is proportional to the engine speed. However, coolant requirements in an engine vary greatly based on many factors during regular operation. With the known variable water pumps, the controls do not always allow for specific flow control levels so that the coolant flow can be optimized for efficient engine performance during the various operating conditions, and instead are generally designed for “off” or “on” operation.

It would be desirable to provide a less complex and more reliable actuator arrangement, and in particular an actuator arrangement that limits the modifications required to an existing water pump housing and bearings, that can be simply controlled and allow variable actuation. The arrangement should also allow more precise flow control, while also maintaining a small space requirement, low weight, and low cost.

SUMMARY

Briefly stated, an external actuator is provided for a variable water pump which includes a housing and variable flow impeller located in the housing that is connected to a drive shaft. The external actuator includes an actuator housing. A drive ring is rotatably mounted in the housing and has external teeth and an internal thread. A drive gear is engaged with the external teeth of the drive ring, the drive gear being rotatably mounted in the actuator housing. A drive nut having external threads is located within the drive ring, with the external threads engaging the internal threads of the drive ring so that rotation of the drive ring causes an axial displacement of the drive nut. At least one actuator pin is connected to the drive nut and is adapted to extend into the water pump housing to the variable flow impeller. A motor is connected to the drive gear for rotation of the drive gear in either direction to vary an output from the variable flow impeller.

In one preferred arrangement, the drive gear is a worm screw, and the external teeth are external worm drive teeth.

Preferably, the variable flow impeller includes an impeller fixed to the drive shaft and an axially displaceable shroud, and the at least one actuator pin is connected to the shroud for axial movement of the shroud in order to vary an output of the water pump. In one preferred arrangement, the pins extend through the housing into the pump chamber and are connected to the shroud and the shroud does not rotate within the water pump. Rotation of the drive ring in a first direction axially displaces the drive nut moving the shroud to a position in which the impeller is covered, reducing or stopping the flow of coolant from the water pump. Rotation of the drive ring in a second direction, opposite the first direction, axially displaces the drive nut in the opposite direction to move the shroud to a position in which the impeller is partially or fully uncovered, depending on the amount of rotation of the drive ring, which is controlled based on the engine operating condition. The position of the ring can be fixed in a fully covered, a fully uncovered, or an intermediate position by the motor.

Using this arrangement, modifications to the existing water pump housing are limited due to the external actuator arrangement located outside of the housing, with only limited modifications to the water pump being required for attachment of the actuator housing and for one or more actuator pins to extend into the housing and actuate the variable flow impeller.

In another aspect, the internal and external threads are multi-lead threads, and the drive ring is adapted to rotate less than 180°. More preferably, the drive ring is adapted to rotate less than 90° in order to actuate the variable flow impeller.

In one preferred embodiment, the actuator housing is mounted to the front of the water pump housing and has a hollow center, and is adapted to be fastened to the water pump housing about the drive shaft. Alternatively, it can be located on the back side of the water pump housing.

Preferably there are a plurality of actuator pins connected to the drive nut.

In order to provide for a fail-safe operation of the water pump, a return spring is preferably located around each of the actuator pins so that the drive nut is biased to a position in which the variable flow impeller provides for full flow of coolant through the water pump. A return spring can also be connected to the drive gear or a shaft supporting the drive gear.

Preferably, the internal and external threads on the drive ring and the drive nut are not self-locking, and the motor and associated worm drive do not prevent fail-safe rotation of the drive ring.

In an alternate arrangement, the shroud is rotatable with the impeller, and the at least one actuator pin is connected to a contact ring that presses against the shroud in order to move the shroud to a deactivated position. Preferably a return spring is provided in order to move the shroud to a position allowing the water pump to provide a full flow of coolant. Preferably, a slide bearing or coating is provided on at least one of the contact ring or the shroud in a contact region between the contact ring and the shroud in order to prevent wear and increase the life of the variable water pump.

In another aspect, a variably actuatable water pump is provided having a pump housing with at least a portion of a pump chamber. A drive shaft extends through the pump housing from a drive side of the water pump to the pump chamber, with a drive wheel connected to a drive side end of the drive shaft. A variable flow impeller is located in the pump chamber, including an axially fixed impeller part connected to the drive shaft and an axially movable shroud, movable relative to the axially fixed impeller part from a first position in which blades connected to the impeller part are exposed in order to pump coolant, to a second position in which the blades are covered in order to prevent pumping of the coolant. An external actuator is connected to the pump housing. The external actuator includes an actuator housing. A drive ring is rotatably mounted in the housing and has external teeth and an internal thread. A drive gear is engaged with the external teeth of the drive ring, the drive gear being rotatably mounted in the actuator housing. A drive nut having external threads is located within the drive ring, with the external threads engaging the internal threads of the drive ring so that rotation of the drive ring causes an axial displacement of the drive nut. At least one actuator pin is connected to the drive nut and extends into the water pump housing and is connected to the axially movable shroud. A motor is connected to the drive gear for rotation of the worm screw in either direction to vary an output from the variable flow impeller.

Preferably, the variable water pump is provided on an internal combustion engine, and the actuator assembly has a hollow center and is adapted to be fastened to the water pump housing about the drive shaft in a space between the drive wheel and the pump housing. This space is typically open in internal combustion engines and thus an actuator can be provided without increasing an axial length of the internal combustion engine arrangement.

Preferably, one or more seals are located between the actuator pin(s) and the pump housing at the areas where the pins enter the pump housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing Summary and the following detailed description will be better understood when read in conjunction with the appended drawings, which illustrate a preferred embodiment of the invention. In the drawings:

FIG. 1 is cross-sectional view through a variable water pump having an external actuator in accordance with the present invention.

FIG. 2 is a partial cross-sectional view taken along line 2-2 through the actuator housing of FIG. 1.

FIG. 3 is a detailed elevational view, in cross-section, of the drive ring used in the external actuator shown in FIG. 1.

FIG. 4 is a perspective detailed view of the drive nut and actuator pins used in the external actuator shown in FIG. 1.

FIG. 5 is a partially exploded schematic view showing an alternate arrangement of the drive nut, actuator pins and a contact ring used to actuate the impeller shroud in a variable water pump.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Certain terminology is used in the following description for convenience only and is not limiting. The words “front,” “rear,” “upper” and “lower” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward and away from the parts referenced in the drawings. “Axially” refers to a direction along the axis of a shaft or rotating part. A reference to a list of items that are cited as “at least one of a, b, or c” (where a, b, and c represent the items being listed) means any single one of the items a, b, or c, or combinations thereof. The terminology includes the words specifically noted above, derivatives thereof and words of similar import.

Referring to FIG. 1, a cross-sectional view through a variable water pump 12 having an external actuator assembly 10 according to an exemplary embodiment is shown. The variable water pump 12 includes a housing 14 with at least a portion of a pump chamber 15 defined therein. The pump chamber 15 can be fully defined by the housing 14 and a portion of the engine block or can be fully formed by the housing 14. A variable flow impeller assembly is provided having an impeller 16 as well as a shroud 18 which can be shifted axially to expose more or less of the vanes of the impeller 16 in order to control the flow of coolant through the water pump 12. The shroud 18 may or may not form a seal with the water pump housing 14 or possibly a volute element (not shown) opposite of the impeller 16, fully cutting off fluid flow to the impeller blades. The impeller 16 is mounted on a drive shaft 22 of the an integral shaft bearing assembly 20, which is provided as a unit including the shaft 22 and the bearings 24 that can be assembled as a unit into the water pump housing 14. A seal 26 is preferably provided around the drive shaft 22 to prevent coolant from escaping from the pump chamber 15 along the drive shaft 22. A drive wheel 28 is preferably connected to a drive side of the drive shaft 22.

The external actuator 10 is preferably mounted to the water pump 12 in an area between the drive wheel 28 and the water pump housing 14. The actuator 10 includes a housing 30 with a flange 32 for attachment to the front of the water pump housing 14, preferably as an integral part.

A drive ring 40 is rotatably mounted in the actuator housing 30. The drive ring 40 has external teeth 44 and an internal thread 42, shown in detail in FIG. 3, located on the inner surface. The external teeth are preferably worm gear teeth 44.

A drive nut 60 having external threads 62 is located within the drive ring 40, with the external threads 62, for example as shown in FIG. 4, engaging the internal threads 42 of the drive ring 40 as shown in FIG. 3 so that rotation of the drive ring 40 causes an axial displacement of the drive nut 60. As shown in FIG. 1, at least one actuator pin 64 is connected to the drive nut 60 and extends through openings 65 in the water pump housing 14 to control the flow of coolant from the variable flow impeller, preferably via being connected to the shroud 18 as shown. In the arrangement of FIG. 1, the shroud 18 is axially movable as indicated by the arrow, but is rotationally fixed. Seals 68 are arranged around the actuator pins 64 in the pump housing 14.

Preferably, the internal and external threads 42, 62 are multi-lead threads, as illustrated for example in FIG. 3, and the drive ring 40 is adapted to rotate less than 180°. In the preferred embodiment shown in FIGS. 1-4, the drive ring 40 is adapted to rotate less than 90° in order to shift the drive nut 60 and the attached actuator pin(s) 64 a sufficient axial distance so that the shroud 18 can be moved between a fully covered position, as shown in FIG. 1, in which the variable water pump flow is restricted due to the vanes of the impeller 16 being covered by the shroud 18, to an uncovered position which the shroud 18 is shifted (to the left from the position shown in FIG. 1) by movement of the drive ring 40 in the in a first rotational direction so that the drive nut 60 is shifted axially and raises the shroud 18. Rotation of the drive ring 40 by the drive gear 36 is therefore used to vary an output from the variable flow impeller.

Return springs 66 are preferably provided around the actuator pins 64 so that in the event of failure of the motor 34, the drive nut 60 is shifted (to the left in FIG. 1) and the shroud 18 uncovers the vanes of the impeller 16 so that the water pump 12 is placed in a fail-safe operating position.

Referring to FIG. 2, the drive part of the electromechanical actuator 10 is shown in detail, and includes a motor 34 with a drive gear 36 connected to the motor 34. The drive gear 36 is preferably a worm screw in the first exemplary embodiment and is rotatably mounted in the housing 30, preferably on a shaft 37 via bearings 38, and intermeshes with the worm gear teeth 44 on the drive ring 40. A controller 70, which can be the ECM or a separate controller operates the motor 34 to drive the drive gear 36 (preferably the worm screw which will also be referred to as 36) in either direction for variable positioning of the shroud 18 in the water pump 12 in order to control or regulate the flow of coolant from the water pump 12 based on engine operating conditions. A torsion spring 39 is preferably connected to the shaft 37 for the worm screw 36 and is wound when the worm screw 36 is driven to a position in which the shroud 18 covers the impeller 16 so that there is sufficient stored torsional energy to move the shroud 18 back off of the impeller 16 to a fail-safe position in the event of a failure of the motor 34.

In addition, the return springs 66 also act to return the drive nut 60 to the fail-safe position. To assist in this, the internal and external threads 42, 62 are not self-locking threads. Accordingly, during a failure of the motor 34, the torsion spring 39 and the return springs 66 can move the drive nut 60 to a position in which the shroud 18 does not cover the vanes on the impeller 16 in order to provide full coolant flow.

In the first preferred embodiment, the variable flow impeller assembly includes the impeller 16 which is fixed to the drive shaft 22 and the shroud 18 is axially displaceable via the actuator pin(s) 64 connected to the drive nut 60. This allows axial movement of the shroud 18 allows control of an output flow from the water pump 12. This arrangement is preferably used in connection with an on/off operation of the variable water pump 12, but could also be used for variable flow rate control.

For a flow regulating arrangement, one preferred alternate arrangement of the water pump and the connection of the actuator 10 to the variable flow impeller assembly is shown in FIG. 5. Only the differences from the arrangement shown in FIG. 1 are shown in detail. Here the drive nut 60′ is shown with actuator pins 64 connected to a contact ring 74. The water pump housing is schematically represented by the dashed line 14, with the seals 68 also being represented around the actuator pins 64 where they extend through the water pump housing 14. The contact ring 74 is adapted to contact the shroud 18′ which is arranged facing away from the drive wheel side of the water pump 12 for axial movement over the impeller 16 which is connected to the drive shaft (not shown in FIG. 5). Preferably, a slide bearing or anti-friction coating indicated at 78 is provided on the contact ring 74. This can be in the form of a PTFE coating or layer. This reduces wear and friction in a contact region between the contact ring 74 and the shroud 18.

A return spring 79 is preferably provided so that the shroud 18′ is biased toward the left in FIG. 5 to a fail-safe position so the vanes of the impeller 16 are exposed in order to pump coolant in the event that the actuator 10 cannot operate. While the spring 79 is shown in one end position, those of ordinary skill in the art will appreciate from the present disclosure that the spring could be located at other axial positions to provide the same effect of biasing the shroud 18′ to the fail-safe position. When a lower coolant flow or no coolant flow is desired, the drive nut 60′ is axially displaced via the actuator assembly 10 so that the shroud 18′ is moved to the right in FIG. 5 against the pressure of the spring 79 partially or fully covering the vanes of the impeller 16 to either regulate or stop the flow of coolant through the water pump 12.

Use of the actuator assembly 10 with the motor driven drive gear, preferably in the form of a worm drive, has the benefit of providing exact positioning that is determinable from the motor 34 position. The actuator 10 can also be located in front of or behind the shroud 18, allowing various packaging configurations.

As an alternative to the motor-worm screw drive, a standard spur gear drive could be utilized as the drive gear 36. This would avoid the need for the torsion spring 39.

The actuator assembly 10 can be provided separately or in conjunction with a water pump 12 providing a variably actuatable water pump assembly including the features of the water pump 12 and the actuator assembly 10. This arrangement provides the ability to have a variable water pump 12 in approximately the same envelope as an existing water pump by utilizing a portion of the space between the drive wheel and the water pump housing. This allows for improvements in engine efficiency and performance while maintaining a small space requirement and low cost.

It is to be appreciated and will be apparent to those skilled in the art that many physical changes, only a few of which are exemplified in the detailed description of the invention, could be made without altering the inventive concepts and principles embodied therein. It is also to be appreciated that numerous embodiments incorporating only part of the preferred embodiment are possible which do not alter, with respect to those parts, the inventive concepts and principles embodied therein. The present embodiment and optional configurations are therefore to be considered in all respects as exemplary and/or illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all alternate embodiments and changes to this embodiment which come within the meaning and range of equivalency of said claims are therefore to be embraced therein. 

What is claimed is:
 1. An external actuator for a variable water pump which includes a housing and a variable flow impeller located in the housing that is connected to a drive shaft, the external actuator comprising: an actuator housing; a drive ring rotatably mounted in the actuator housing, the drive ring having external teeth and an internal thread; a drive gear engaged with the external teeth of the drive ring, the drive gear being rotatably mounted in the actuator housing; a drive nut having external threads located within the drive ring with the external threads engaging the internal threads of the drive ring so that rotation of the drive ring causes an axial displacement of the drive nut; at least one actuator pin connected to the drive nut that is adapted to extend into the water pump housing to the variable flow impeller; and a motor connected to the drive gear for rotation of the gear in either direction to vary an output from the variable flow impeller.
 2. The external actuator for a variable water pump of claim 1, wherein the drive gear is a worm screw and the external teeth are worm gear teeth.
 3. The external actuator for a variable water pump of claim 2, further comprising a torsion spring connected to a shaft supporting the worm screw.
 4. The external actuator for a variable water pump of claim 1, wherein the internal and external threads are multi-lead threads, and the drive ring is adapted to rotate less than 180° for actuation.
 5. The external actuator for a variable water pump of claim 4, wherein the drive ring is adapted to rotate less than 90°.
 6. The external actuator for a variable water pump of claim 1, wherein the actuator housing has a hollow center, and is adapted to be fastened to the water pump housing about the drive shaft.
 7. The external actuator for a variable water pump of claim 1, wherein there are a plurality of the actuator pins, and a return spring is located around each of the actuator pins that are adapted to move the drive nut to a failsafe position.
 8. The external actuator for a variable water pump of claim 1, wherein the internal and external threads are not self-locking.
 9. The external actuator for a variable water pump of claim 1, wherein the variable flow impeller includes an impeller fixed to the drive shaft and an axially displaceable shroud, and the at least one actuator pin is adapted to be connected to the shroud for axial movement of the shroud in order to vary an output of the water pump.
 10. The external actuator for a variable water pump of claim 9, wherein the shroud is rotatable with the impeller, and the at least one actuator pin is connected to a contact ring that presses against the shroud.
 11. A variably actuatable water pump, comprising: a pump housing having at least a part of a pump chamber; a drive shaft extending through the pump housing from a drive side of the water pump to the pump chamber, with a drive wheel connected to a drive side end of the drive shaft; a variable flow impeller located in the pump chamber, including an axially fixed impeller part connected to the drive shaft and an axially movable shroud, movable relative to the axially fixed impeller part from a first position in which blades connected to the impeller part are exposed in order to pump coolant, to a second position in which the blades are covered in order to prevent pumping of the coolant; an external actuator connected to the pump housing, including: an actuator housing; a drive ring rotatably mounted in the actuator housing, the drive ring having external teeth and an internal thread; a drive gear engaged with the external teeth of the drive ring, the drive gear being rotatably mounted in the actuator housing; a drive nut having external threads located within the drive ring with the external threads engaging the internal threads of the drive ring so that rotation of the drive ring causes an axial displacement of the drive nut; at least one actuator pin connected to the drive nut that extends into the water pump housing to the variable flow impeller; and a motor connected to the drive gear for rotation of the gear in either direction to vary an output from the variable flow impeller.
 12. The variable water pump of claim 11, wherein the actuator housing has a hollow center, and is adapted to be fastened to the water pump housing about the drive shaft in a space between the drive wheel and the pump housing.
 13. The variable water pump of claim 11, further comprising a seal located between the at least one actuator pin and the pump housing.
 14. The variable water pump of claim 11, further comprising a return spring located around the at least one actuator pin that presses against the pump housing and the drive nut to move the drive nut and the shroud to the first position as a failsafe. 